The present invention relates to a textile substrate, which can be processed to form coverings for upholstered furniture, chairs and other seats and in which the substrate has at least one yarn, which is constructed as a mixed yarn having natural fibers.
Special demands have been typically made on material layers to be used for seat coverings. The term "seat" is used to define all types thereof, i.e. upholstered furniture, covered chairs, car seats, office chairs, as well as seats in vehicles, such as aircraft and trains, as well as for wheel-chairs for invalids and handicapped.
The demands to be made on such materials are of widely differing types and in part also have opposite tendencies, i.e. an improvement to one characteristic leads to a deterioration of another.
The sitting comfort resulting from such coverings is particularly important when the seat is used for considerable periods, without the user being able to leave it. Such a situation e.g. occurs with invalids confined to wheel-chairs, the invalid only being able to leave the chair with external aid. A similar situation exists with the driver of a motor vehicle, if he has to cover long distances without being able to interrupt the journey. Similar conditions also exist for aircraft and rail travellers, which involve long periods during which the traveller sits.
Even when sitting, the human body evolves heat, which is given off to the environment. The amount of heat to be dissipated is dependent on the heat resistance of the environment. If this is too high, the body is unable to maintain its heat balance, which leads to perspiration which cools the body. If this perspiration is insignificant and hardly detectable, then it does not lead to discomfort for the person involved. However, in the case of significant perspiration it leads to liquid formation, then the seat feels unpleasant if it is not possible to remove the moisture. The well-being of the person seated for a long time depends both on the clothing and in particular on the seat covering and the heat resistance thereof.
It has been known to use in the clothing field the materials which have a low heat resistance and therefore facilitate perspiration of the body to the outside and largely prevent the penetration of wind and rain. Such articles of clothing consist of a laminate, where use is made of two or three layers. One of these layers is a thin membrane of polytetrafluoroethylene (PTFE), which contains microscopically small pores. The small pores of this water-repelling membrane do not permit penetration of water therethrough. However, it is possible for water vapor, such as is produced through the heat evolution of the human body, to diffuse through the pores.
However, such laminates cannot be used for seats, because the water vapor forming on the body reaches the outer surface of the covering and would have to be given off to the environment. However, as substantially all seats have an upholstery comprising plastic inserts and foams, which have a high heat resistance, the water vapor passing through the membrane can only be given off to a minor extent, if at all, to the environment.